1. Field of the Invention
The present invention relates to a network management apparatus and a method of controlling the same, and a communication apparatus and a method of controlling the same.
2. Description of the Related Art
Conventionally, there is known a photographing network system such as a wireless photographing system with multiple flashes in which a plurality of apparatuses connected via a network cooperatively perform a photographic operation. Each of the apparatuses that form such a photographing network system has functions for implementing the network between the apparatuses and functions for implementing the cooperative photographic operation. The photographing network system can be considered to include two internal logic systems: a network system formed by the functions of the apparatuses concerning the network and a photographing system formed by the functions concerning the photographic operation. Each internal system is implemented based on the master/slave relationship between a main apparatus and a sub-apparatus.
More specifically, the network system is formed from a management apparatus (main apparatus) for managing the network and a terminal (sub-apparatus) other than the management apparatus. The photographing system is formed from a master apparatus (main apparatus) for issuing a control command to control a photographic operation and a slave apparatus (sub-apparatus) for executing the issued control command to control a photographic operation.
Each apparatus that forms the photographing network system can operate as the main apparatus or sub-apparatus in each system. Conventionally, whether an apparatus should operate as the main apparatus or sub-apparatus in each logic system is determined independently for each system. For example, an apparatus operates as the management apparatus in the network system and as a slave apparatus in the photographing system. Another apparatus operates as a terminal in the network system and as the master apparatus in the photographing system.
A method of controlling each apparatus forming a network in consideration of the master/slave relationship has been proposed. Japanese Patent Laid-Open No. 2004-274625 discloses a photographing system including a main photographing apparatus and a sub photographing apparatus that performs a photographic operation based on a command from the main photographing apparatus. An apparatus that has issued a request first or an apparatus determined based on a predetermined priority order out of apparatuses that have issued a request simultaneously is used as the main photographing apparatus.
Japanese Patent Laid-Open No. 2007-81811 proposes a method of maintaining an ad hoc network in which one of communication terminals operates as a management terminal, and the communication terminals other than the management terminal operate as general terminals. More specifically, a general terminal having a low communication error rate is selected as a management terminal candidate. In case of the absence of the management terminal, the general terminal selected as the management terminal candidate is operated as a new management terminal.
As described above, each apparatus that forms the photographing network system to be discussed in the present invention is affected by both the master/slave relationship in the network system and the master/slave relationship in the photographing system. For this reason, for example, if the management apparatus in the network system has gone, it is not preferable to maintain the network simply considering the master/slave relationship of the remaining apparatuses in the network system. Similarly, when the master apparatus of the photographing system has left from the network system, it is difficult to maintain the network system without considering the master/slave relationship in the network system.
However, neither of Japanese Patent Laid-Open Nos. 2004-274625 and 2007-81811 discloses or suggests a photographing network system itself that is formed from apparatuses affected by the two independent master/slave relationships. How to appropriately maintain the network in consideration of the two master/slave relationships in the case of absence of the network management apparatus in the photographing network system to be discussed in the present invention is conventionally unknown.